Analysis, control and augmentation of microcantilever deflections in bio-sensing systems (original) (raw)
Related papers
Design and Analysis of Microcantilevers for Biosensing Applications
Journal of the Association for Laboratory Automation, 2003
W e have analyzed the detection of microcantilevers utilized in biosensing chips. First, the primary deflection due to the chemical reaction between the analyte molecules and the receptor coating, which produces surface stresses on the receptor side is analyzed. Oscillating flow conditions, which are the main source of turbulence in cantilever based biosensing chips, are found to produce substantial deflections in the microcantilever at relatively large frequency of turbulence. Then mechanical design and optimization of piezoresistive cantilevers for biosensing applications is studied. Models are described for predicting the static behavior of cantilevers with elastic and piezoresistive layers. Chemo-mechanical binding forces have been analyzed to understand issues of saturation over the cantilever surface. Furthermore, the introduction of stress concentration regions during cantilever fabrication has been discussed which greatly enhances the detection sensitivity through increased surface stress, and novel microcantilever assemblies are presented for the first time that can increase the deflection due to chemical reaction. Finally an experiment was made to demonstrate the shift of resonant frequency of cantilever used as biosensor. The relation between resonant frequency shift and the surface stress was analyzed.
Calculation of Stress And Deflection In Double Layer Microcantilever For Biosensor Application
Lia Aprilia, Ratno Nuryadi, Djoko Hartanto, 2013
In microcantilever-based biosensor, a sensitive layer plays an important role as a place for the establishment of functional layer for detecting molecules target. When a sensitive layer is coated on the microcantilever surface, a surface stress change is induced as a consequence of adsorbate-surface interaction, resulting in a deflection of the microcantilever. However, the microcantilever with the sensitive layer of gold (Au) or 3-Aminopropyltriethoxysilane (aminosilane) which are commonly used in biosensor, has not been reported. In this paper, we study a dependence of the microcantilever deflection on the gold / aminosilane layers thickness in static mode operation. From a derivation of Stoney equation, it is found that the influence of material properties on the deflection of double layer microcantilever from the film stress and radius of curvature. Such relationship is important because the microcantilever deflection directly influences the sensor sensitivity. Our results indicate that the material and the thickness of sensitive layer should be considered to obtain a high sensitivity of microcantilever sensor.
Effects of design parameters on sensitivity of microcantilever biosensors
IEEE/ICME International Conference on Complex Medical Engineering, 2010
Microcantilever biosensors produce cantilever bending due to differential surface stress between upper and lower surfaces of the cantilever. The bending is associated with concentration of ligands and adsorbed ligand-receptor intermolecular forces. Sample volume sizes in clinical diagnostic applications are usually very minute requiring a highly sensitive microcantilever for disease detection. This paper investigates a number of parameters that influence the sensitivity of microcantilever biosensors. The parameters include length, thickness, shape, and material of the cantilever beam. Biosensors of varying parameters are modeled and simulated. The results show that increasing the length of the cantilever beam enhances its sensitivity. However, increasing the thickness of the cantilever beam reduces its sensitivity. In static analysis, the shape of the cantilever beam does not notably impact upon its sensitivity. Also, using materials with lower Young's modulus improves the sensitivity.
Biosensors Based on Cantilevers
Methods in Molecular Biology, 2009
Microcantilevers based-biosensors are a new label-free technique that allows the direct detection of biomolecular interactions in a label-less way and with great accuracy by translating the biointeraction into a nanomechanical motion. Low cost and reliable standard silicon technologies are widely used for the fabrication of cantilevers with well-controlled mechanical properties. Over the last years, the number of applications of these sensors has shown a fast growth in diverse fields, such as genomic or proteomic, because of the biosensor flexibility, the low sample consumption, and the non-pretreated samples required. In this chapter, we report a dedicated design and a fabrication process of highly sensitive microcantilever silicon sensors. We will describe as well an application of the device in the environmental field showing the immunodetection of an organic toxic pesticide as an example. The cantilever biofunctionalization process and the subsequent pesticide determination are detected in real time by monitoring the nanometer-scale bending of the microcantilever due to a differential surface stress generated between both surfaces of the device.
At the microscale, cantilever vibrations depend not only on the microstructure's properties and geometry but also on the properties of the surrounding medium. In fact, when a microcantilever vibrates in a fluid, the fluid offers resistance to the motion of the beam. The study of the influence of the hydrodynamic force on the microcantilever's vibrational spectrum can be used to either (1) optimize the use of microcantilevers for chemical detection in liquid media or (2)extract the mechanical properties of the fluid. The classical method for application (1) in gas is to operate the microcantilever in the dynamic transverse bending mode for chemical detection. However, the performance of microcantilevers excited in this standard out-of-plane dynamic mode drastically decreases in viscous liquid media. When immersed in liquids, in order to limit the decrease of both the resonant frequency and the quality factor, alternative vibration modes that primarily shear the fluid (rather than involving motion normal to the fluid/beam interface) have been studied and tested: these include inplane vibration modes (lateral bending mode and elongation mode). For application ,the classical method to measure the rheological properties of fluids is to use a rheometer. To overcome the limitations of this classical method, an alternative method based on the use of silicon microcantilevers is presented. The method, which is based on the use of analytical equations for the hydrodynamic force, permits the measurement of the complex shear modulus of viscoelastic fluids over a wide frequency range.
Simulation and design of piezoelectric microcantilever chemical sensors
2005
This paper presents an analytical modeling of a piezoelectric multi-layer cantilever used as a micro-electro-mechanical-system (MEMS) chemical sensor. Selectively coated microcantilevers have been developed for highly sensitive chemical sensor applications. The proposed piezoelectric chemical sensor consists of an array of multi-layer piezoelectric cantilevers with voltage output in the millivolt range that replaces the conventional laser-based position-sensitive detection systems. The sensing principle is based upon changes in the deflection induced by environmental factors in the medium where a microcantilever is immersed. Bending of the cantilever induces the potential difference on opposite sides of the piezoelectric layer providing an information signal about the detected chemicals. To obtain an application specific optimum design parameters and predict the cantilever performance ahead of actual fabrication, finite element analysis (FEM) simulations using CoventorWare (a MEMS design and simulation program) were performed. Analytical models of multi-layer cantilevers as well as simulation concept are described. Both mechanical and piezoelectric simulation results are carried out. The cantilever structures are analyzed and fabrication process steps are proposed.
Fabrication of piezoresistive microcantilever using surface micromachining technique for biosensors
2005
A microcantilever-based biosensor with piezoresistor has been fabricated using surface micromachining technique, which is cost effective and simplifies a fabrication procedure. In order to evaluate the characteristics of the cantilever, the cystamine terminated with thiol was covalently immobilized on the gold-coated side of the cantilever and glutaraldehyde that would be bonded with amine group in the cystamine was injected subsequently. This process was characterized by measuring the deflection of the cantilever in real time monitoring. Using a piezoresistive read-out and a well-known optical beam deflection method as well, the measurement of deflection was carried out. The sensitivity of piezoresistive method is good enough compared with that of optical beam deflection method.
Sensors and Actuators B: Chemical, 2014
Hydrogen is a key parameter to monitor radioactive disposal facility such as the envisioned French geological repository for nuclear wastes. The use of microcantilevers as chemical sensors usually involves a sensitive layer whose purpose is to selectively sorb the analyte of interest. The sorbed substance can then be detected by monitoring either the resonant frequency shift (dynamic mode) or the quasi-static deflection (static mode). The objective of this paper is to demonstrate the feasibility of eliminating the need for the sensitive layer in the dynamic mode, thereby increasing the long-term reliability. The microcantilever resonant frequency allows probing the mechanical properties (mass density and viscosity) of the surrounding fluid and, thus, to determine the concentration of a species in a binary gaseous. Promising preliminary work has allowed detecting concentration of 200ppm of hydrogen in air with non-optimized geometry of silicon microcantilever with integrated actuation and read-out.
The spring constant calibration of the piezoresistive cantilever based biosensor
2010
Piezoresistive microcantilevers are widely applied to measurements of low forces, masses and viscosity. After surface functionalization they might be used as a biochemical sensors being capable of the intermolecular force investigation. The problem is that such sensors change its mechanical properties in the environment they operate. Therefore there is a need for a high accuracy technique being capable of measuring of mechanical properties of functionalized cantilevers operating in the target environment. We suppose that such conditions meet the analysis of thermomechanical oscillation noise.